Electronics fight club: Can gallium nitride sock it to silicon?

Silicon has been reigning the electronics world for so long that maybe it’s no surprise that other materials are attempting to grab the crown.

Just last year I reported on such attempts by phase change materials and correlated oxides. While advances in research are one thing, however, the true measure of whether an alternative material can take on silicon lies in the market.

And in that market, gallium nitride is starting to look like a strong contender.

MIT spinout company Cambridge Electronics Inc. (CEI) is helping gallium nitride get into the center ring with its recent announcement of “a line of GaN transistors and power electronic circuits that promise to cut energy usage in data centers, electric cars, and consumer devices by 10 to 20 percent worldwide by 2025,” according to an MIT News article.

CEI is putting gallium nitride transistors in power electronics, tech that controls and converts electric power—such as that hefty power pack on your laptop charging cord.

You know how that power pack heats up after supplying the battery with a full charge? That heat is wasted energy.

Many current power electronics use silicon transistors, which switch on and off really well to regulate the voltage flowing through the device. But silicon transistors are less ideal in terms of resistance, which, like mechanical friction, generates that heat.

The MIT News article contends that “CEI’s GaN transistors have at least one-tenth the resistance of such silicon-based transistors, according to the company. This allows for much higher energy-efficiency, and orders-of-magnitude faster switching frequency—meaning power-electronics systems with these components can be made much smaller. CEI is using its transistors to enable power electronics that will make data centers less energy-intensive, electric cars cheaper and more powerful, and laptop power adapters one- third the size—or even small enough to fit inside the computer itself.”

A prototype laptop power adapter made by Cambridge Electronics using GaN transistors. At 1.5 cubic inches in volume, this is the smallest laptop power adapter ever made. Credit: Cambridge Electronics

Earlier this year, we started to see other companies joining the GaN transistor party, too, with products that could compete with the price of silicon.

Although GaN chips themselves are nothing new, the technology had some significant hurdles to overcome before being feasible in a commercial market.

Part of the reason why the transistors are now competitive is due to significant advances in technology and manufacturing methods that allow GaN to be efficient and cost-effective at the same time.

Transistors need to be able to be switched between an on and off state, like a switch. In the on position, transistors allow current to pass through, while the off position passes no current. To protect electronic devices, transistors not only need to be able to switch efficiently, but they also need to default to the off state to protect from short circuits and other hazards.

But GaN is inherently switched on, so it needs some adjustments to change the material’s structure. “We always talk about GaN as gallium and nitrogen, but you can modify the basic GaN material, add impurities and other elements, to change its properties,” Tomás Palacios, CEI co-founder and MIT associate professor of electrical engineering and computer science, says in the release.

The team found that if it layered different materials to create the transistors, it could engineer GaN transistors that switch off by default. [I contacted Palacios to request more information about these materials, but haven’t received a response.]

In addition to changing the materials, the team also tweaked the process to grow GaN transistors, making fabrication cost-effective.

“Basically, we are fabricating our advanced GaN transistors and circuits in conventional silicon foundries, at the cost of silicon. The cost is the same, but the performance of the new devices is 100 times better,” CEI vice president for device development Bin Lu says in the release.

CEI now offers GaN devices and chips for sale, but the company also is developing laptop power adaptors—with a volume of just 1.5 cubic inches—that use more efficient GaN transistors to allow such a compact size.

Beyond consumer electronics, however, the team also says that GaN transistors will propel future electric vehicles further.

“The silicon transistors used today have a constrained power capability that limits how much power the car can handle,” the MIT news article states. “This is one of the main reasons why there are few large electric vehicles. GaN-based power electronics, on the other hand, could boost power output for electric cars, while making them more energy-efficient and lighter—and, therefore, cheaper and capable of driving longer distances.”

There are other signs, too, that GaN may have a fighting chance.

In addition to the Department of Energy’s 2013 investment of $140 million in PowerAmerica—a research institute dedicated to power electronics, of which half is centered on GaN—the University of Arkansas’s Grid-connected Advanced Power Electronic Systems Center (GRAPES) just received a $200,000 NSF grant to study modeling of GaN devices.

Imec is extending its gallium nitride-on-silicon R&D. Credit: Imec

And nanoelectronics research center Imec (formerly Interuniversity Microelectronics Centre) is also extending its reach into GaN technology with the expansion of the center’s Galium Nitride-on-Silicon R&D program, in an effort to bring GaN technologies closer to commercialization. According to the center’s press release, “Imec welcomes new partners interested in next generation GaN technologies and companies looking for low-volume manufacturing of GaN-on-Si devices to enable the next generation of more efficient and compact power converters.”

Market reports are predicting huge growth in the market for GaN power semiconductors, with figures reaching 60–80% annual growth in the near future. Compounding that exponential growth over the next few years, reports suggest a $1.75 billion market value by 2022.

So will GaN one day reign supreme? No matter what the outcome, it’s looking like it will at least be a good fight.